This invention relates to dry well temperature test systems and to systems particularly designed to be portable for easy use on site in testing and calibration of various temperature sensing devices, such as thermo-couples, thermo-switches, thermistors, thermometers, temperature control systems, and temperature indicators. Several prior art systems are shown in U.S. Pat. Nos. 3,699,800; 3,738,174; and 3,939,687.
The prior art devices include an electrically heated, dry temperature well for receiving the probe or other temperature sensing device which is to be tested or calibrated. The devices also include some means for setting the desired temperature, a control circuit for controlling the input to the well to obtain the desired temperature, and some means for indicating that the desired temperature has been obtained. However, these prior art devices have operated only at elevated temperatures, that is at temperatures higher than ambient. It is an object of the present invention to provide a new and improved temperature calibration system which can operate at temperatures below ambient as well as above ambient, that is, to provide a system that can produce cooling to a predetermined temperature as well as heating to a predetermined temperature. One embodiment of the present invention is operable over the range of minus 40.degree. to plus 250.degree. F. Other objects, advantages, features and results will more fully appear in the course of the following description.